This paper presents a new robot actuator using LaNi_{4, 5}Al_0.5 as metal hydride. It is a force output type actuator consisting of a heater, a metal hydride container, and a bellows. The metal hydride has an unique energy conversion property. Thermal energy can be converted into mechanical energy. Therefore, the desorption and absorption of hydrogen can be controlled by heating and cooling the metal hydride and the bellows can be moved by the hydrogen pressure. Also, this servo actuator has a pressure feedback control system using a PID controller to improve the response characteristics. The pressure feedback control system is synthesized by using the model simulation of the controlled system.
Actually, this force output type servo actuator system was examined.
As a result, the following facts can be specifically pointed out:
1) The developed simulator can be useful for designing a metal hydride actuator with the higher performance.
2) Nonlinearity of metal hydride characteristics is not a serious problem. In addition, the heater saturation can be compensated by using a PID controller with antireset windup.
3) The impedance matching of this actuator is relatively good. The detailed analysis of this point, however, is a matter for further research in order to match a metal hydride actuator to loads over a wide range.